Selective Detection Of Nitroaromatic Explosives Research Articles

Regulation on the ligand fluorescence in UiO-66-Y metal-organic frameworks for effective detection of nitro-aromatic explosives

Rapid, sensitive and highly selective detection of nitro-aromatic explosives (NAEs) has become one of the most pressing environmental and safety issues. Metal-organic frameworks (MOFs) offer new possibilities for the development of new photoactive materials with excellent sensing properties. In this paper, three robust UiO-66-type fluorescent MOFs were prepared from the self-assembly of yttrium cations (Y3+) and linear dicarboxylic acid ligands, named terephthalic acid (BDC), 2-hydroxyterephthalic acid (OHBDC) and 2,5-dihydroxyterephthalic acid (DHBDC). The solid and solution fluorescence properties of three MOFs were successfully modulated by regulating the number of –OH functional groups from zero to two. At 370 nm excitation, Y-BDC MOF without –OH group was almost non-fluorescent, Y-OHBDC MOF with one –OH group emitted blue fluorescence, and Y-DHBDC MOF with two –OH groups emitted green fluorescence. Thanks to the suitable porous structures and stable frameworks, Y-OHBDC and Y-DHBDC MOFs both can quantificationally detect at least seven nitro-aromatic explosives (NAEs) by a fluorescence quenching process. Remarkably, the detection performance for 2,4,6-trinitrophenol (TNP) is the most outstanding with the KSV values of 8.4 × 104 M−1 and 2.1 × 105 M−1. Fast response, high sensitivity, strong anti-interference ability and good reusability make UiO-66-Y MOFs potential fluorescent sensors for TNP.

Rational design of AIE-active biodegradable polycarbonates for high-performance WLED and selective detection of nitroaromatic explosives

Luminescent polymers have garnered considerable research attention for their excellent properties and wide range of applications in multi-responsive materials, bioimaging, and photoelectric devices. Thereout, various modulations of polymer structure are often the main approach to obtaining materials with different luminescent colors and functions. However, polymers with biodegradability, tunable color, and efficient emission simultaneously remain a challenge. Herein, we report a feasible strategy to achieve degradable and highly emissive polymers by exquisite combination and interplay of aggregation-induced emission (AIE) unit and environmental-friendly epoxide/CO2 copolymerization. A series of polycarbonates P-TEPxCNy (x = 0, 1, 2, 4, 30, 120; y = 0, 1) were prepared, with emission color changed from blue to yellow by controlling the proportion of two designed AIE-active monomers. Among them, Using P-TCN as emitting layer, high performance white light-emitting diode (WLED) device with an external quantum efficiency (EQE) of 26.09% and CIE coordinates of (0.32, 0.32) was achieved. In addition, the designed polymers can be used as selective sensors for nitroaromatic compounds in their nanoaggregate states.

Photophysical and Fluorescence Nitroaromatic Sensing Properties of Methylated Derivative of a Pamoic Acid Ester.

Rapid and selective detection of nitroaromatic explosives is very important for public safety, life, and environmental health. Current instrumental techniques suffer from high cost and poor site used. In order to investigate fluorescence sensing of nitroaromatics, we prepare a new small fluorescence probe derived from pamoic acid. This study covers the synthesis of Pamoic acid based [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) material and characterization of its structure. The methylation of Pamoic acid ester, which we have successfully synthesized in our previous studies, was carried out in this study. Determination of the photophysical and fluorescent nitroaromatic detection properties of the compound forms the basis of the study. Structural characterization of the synthesized compound [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) was characterized using spectroscopic methods. In addition, Molecular structure of the synthesized compound was determined by single crystal X-ray diffraction studies. In the final step, compounds [diisopropyl 4,4'-methylenebis(3-hydroxy-2-naphthoate)] (1) and [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) were tested as fluorescent probes for the detection of some nitroaromatic explosives. It is seen that Nitrobenzene provides the best quenching effect on the compound [diisopropyl 4,4'-methylenebis(3-hydroxy-2-naphthoate)] (1) containing the -OH group, with lowest the limit of detection (LOD) value. It was observed that Picric acid provided the best quenching effect with lowest the limit of detection (LOD) value in the compound [diisopropyl 4,4'-methylenebis(3-methoxy-2-naphthoate)] (2) obtained by methylation of the -OH group in the compound [diisopropyl 4,4'-methylenebis(3-hydroxy-2-naphthoate)] (1).

Conjugated Polymer Nanoparticles Based on Anthracene and Tetraphenylethene for Nitroaromatics Detection in Aqueous Phase

The sensitive and selective detection of nitroaromatic explosives is of great significance to national security and human health. Herein, the novel linear polymer l-PAnTPE and cross-linked polymer PAnTPE nanoparticles based on anthracene and tetraphenylethene groups were designed and successfully synthesized via Suzuki-miniemulsion polymerization. The particle sizes of the polymers are around 73 nm, making them well dispersible in water. The cross-linked polymer PAnTPE exhibits porous structure, which is beneficial for the diffusion/adsorption of analytes. The fluorescence sensing towards nitroaromatics was performed in the aqueous phase, and l-PAnTPE and PAnTPE nanoparticles showed different quenching degree towards different nitroaromatics. Among them, the quenching constant KSV values of l-PAnTPE and PAnTPE towards 2,4,6-trinitrophenol (TNP) reach 1.8 × 104 M−1 and 4.0 × 104 M−1, respectively, which are 1–2 orders of magnitude higher than other nitroaromatic explosives, thus demonstrating the high sensitivity and selectivity of TNP detection in the aqueous phase. The sensing mechanism was further discussed to clarify this phenomenon by analyzing UV–Vis absorption, excitation, fluorescence spectra, cyclic voltammograms and fluorescence decay measurements. In addition, the paper strips tests exhibit that l-PAnTPE and PAnTPE have great potential in the application of fast, low-cost and on-site nitroaromatics detection.

AIE or AIE(P)E-active transition metal complexes for highly sensitive detection of nitroaromatic explosives

Nitroaromatic compounds (NACs) that are components of explosives have become seriously endanger human health, environmental cleaning, national homeland security, etc. The development of appropriate probes for the detection of NACs with desired easy operability, rapid response, reusability and high sensitivity and selectivity advantages has remained a great challenge. Over the past few years, great efforts have been made toward the development of advanced functional materials based on aggregation-induced emission or aggregation induced emission (phosphorescence) enhancement (AIE or AIE(P)E)-active transition metal complexes(AIEgens)and their remarkable achievements in the detection of NACs due to their high quantum yield and tunable photophysical properties. In this review, a brief description of luminescent AIEgens is presented, accompanied by a study on the Ir(III), Re(I) and Pt(II)-based AIEgens as sensing materials for nitroexplosives detection. Then, the trends and challenges of AIE or AIE(P)E-active transition metal complexes for the sensitive and selective detection of nitroaromatic explosives are also discussed.

A Simple Determination of Trinitrotoluene (TNT) Based on Fluorescence Quenching of Rhodamine 110 with FRET Mechanism.

Sensitive and selective detection of nitroaromatic explosives is an important issue in regard to human health, environment, public security and military issues. In this study, a simple and sensitive fluorescence quenching - based assay utilizing Rhodamine 110 as fluorophore probe was developed for the determination of trinitrotoluene (TNT). This sensitive fluorometric method could measure the decrease in fluorescence of Rhodamine 110 (λex = 490nm, λem = 521nm) owing to the primary amine groups of Rhodamine 110 (different from other rhodamines) capable of donor-acceptor interaction with TNT. The resulting TNT-amine complex can strongly quench the fluorescence emission of Rhodamine 110 by fluorescence resonance energy transfer (FRET) which occurs as the excited Rhodamine 110 fluorophore (donor) transfers its energy to TNT (acceptor) by non-radiative dipole-dipole interaction. Fluorescence quenching varied linearly with TNT concentration, with LOD and the LOQ of 0.71 and 2.38mg L- 1 TNT, respectively. Similar explosives, common soil ions, and possible camouflage materials were found not to interfere with the proposed method, offering significant advantages with its easy methodology, low-cost, sensitivity, and rapidity of analysis. FRET mechanism based on dye donor-TNT acceptor interaction.

Tetraphenylethene probe based fluorescent silica nanoparticles for the selective detection of nitroaromatic explosives.

A simple and sensitive fluorometric method is developed utilizing aggregation-induced emission probe based silica nanoparticles for the detection of nitroaromatic explosives. A positively charged tetraphenylethene based probe (TPE-C2-2+) is doped into silica nanoparticles exploiting electrostatic interactions to produce TPE-SiO2 nanoparticles with a uniform particle size. The TPE-SiO2 nanoparticles exhibit strong fluorescence emission due to the aggregation-induced emission (AIE) effect of the doped TPE probe. The fluorescence emission of TPE-SiO2 offers quantitative and sensitive response to picric acid (PA), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) which are used as model examples of nitroaromatic compounds. The fluorescence spectroscopy results show that the fluorescence emission of TPE-SiO2 was greatly quenched in the presence of the electron-poor nitroaromatic compounds due to the inner filter effect (IFE) and possibly the contact quenching mechanism. TPE-SiO2 nanoparticles show better sensitivity towards PA and could detect PA down to 0.01 μM with a linear detection range of 0.1-50 μM. The increased chemical stability, efficient high sensitivity and simple synthesis of the TPE-SiO2 nanoparticles demonstrate that they can be used as an excellent fluorescent probe for a wide range of electron-poor compounds, i.e. nitroaromatic compounds. Interference studies show that common interfering species with nitroexplosives such as acids, bases, volatile organic compounds, and salt solutions have a negligible effect during the sensing process.

A supramolecular approach towards strong and tough polymer nanocomposite fibers.

Polymer nanocomposite fibers are important one-dimensional nanomaterials that hold promising potential in a broad range of technological applications. It is, however, challenging to organize advanced polymer nanocomposite fibers with sufficient mechanical properties and flexibility. Here, we demonstrate that strong, tough and flexible polymer nanocomposite fibers can be approached by electrospinning of a supramolecular ensemble of dissimilar and complementary components including flexible multiwalled carbon nanotubes (CNT), and stiff cellulose nanocrystals (CNC) in an aqueous poly(vinyl alcohol) (PVA) system. CNT and CNC are bridged by a water-soluble aggregation-induced-emission (AIE) molecule that forms π–π stacking with CNT via its conjugated chains, and electrostatic attraction with CNC through its positive charges leading to a soluble CNT–AIE–CNC ensemble, which further assembles with PVA through hydrogen bonds. A high level of ordering of the nanoscale building blocks combined with hydrogen bonding leads to a more efficient stress transfer path between the reinforcing unit and the polymer. The nanocomposite fiber mat is capable of selective detection of nitroaromatic explosives.

Rational molecular design of aggregation-induced emission cationic Ir(iii) phosphors achieving supersensitive and selective detection of nitroaromatic explosives

Employing AIE-active cationic Ir(iii) phosphors as sensors, the supersensitive and selective detection of TNP was achieved.

H-Bonding Interactions Induced Two Isostructural Cd(II) Metal-Organic Frameworks Showing Different Selective Detection of Nitroaromatic Explosives.

Two luminescent Cd(II) metal-organic frameworks (MOFs) were prepared from electron-rich π-conjugated fluorescent ligands. They are isostructural with sql nets. Their strong luminescences can be quenched by a series of nitroaromatic explosives. Notably, MOF 1 shows highly selective and sensitive detection of 4-nitrophenol (4-NP), while MOF 2 exhibits good responses toward picric acid (PA) compared with other nitroaromatic explosives. This different order of quenching efficiency is because there are H-bonding interactions between MOF 1 and 4-NP, while MOF 2 lacks these H-bonding interactions. MOF 1 displays highly selective and sensitive detection of 4-NP with the high quenching constant (6.74× 104 M-1) and low detection limit (34.48 ppb), which is better than those of known MOFs. MOF 1 and MOF 2 have highly sensitive and selective detection of 4-NP and PA in the practical application, respectively.

Selective detection of picric acid by a fluorescent ionic liquid chemosensor

A fluorescent ionic liquid with a dansylamide chromophore was designed and synthesized, which exhibited strong green fluorescence both in the solution and in the condensed phase. As a fluorescent sensor, this ionic probe showed highly sensitive and selective detection of nitroaromatic explosives, especially for picric acid (PA). Theoretical calculations and NMR studies have demonstrated that a ground-state charge transfer through a protonation process and favorable electrostatic π–π interactions between ionic probe and PA may be responsible to the fluorescence quenching mechanism. Moreover, the resonance energy transfer (RET) studies explained the higher sensitivity and selectivity of this ionic probe towards PA than other nitro-containing explosives. A fluorescent test paper was also prepared for the on-site and accurate detection of PA, which provided a new clue of thoughts for instant and highly selective detection of nitroaromatic explosives.

POSS-based organic–inorganic hybrid nanomaterials: aggregation-enhanced emission, and highly sensitive and selective detection of nitroaromatic explosives in aqueous media

Two organic–inorganic hybrid nanomaterials were prepared and were used as chemosensors for the selective detection of nitroaromatic explosives in aqueous media.

Solvent-induced construction of two zinc metal–organic frameworks for highly selective detection of nitroaromatic explosives

Two three-dimensional metal–organic frameworks 1 and 2 based on p-terphenyl-3,4′′,5-tricarboxylic acid (H3TPT) were synthesized by controlling the solvent media. These two MOFs exhibit high efficiency for the recyclable detection of nitroaromatic compounds.

AIE-active tetraphenylethene functionalized metal-organic framework for selective detection of nitroaromatic explosives and organic photocatalysis.

AIE-active luminogen tetraphenylethene (TPE) was incorporated into a UiO-isoreticular zirconium metal-organic framework via the strategy of mixed dicarboxylate struts, and the resulting functionalized MOF shows a strong blue-green emission and selective sensing of nitroaromatic explosives 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenol (DNP) through fluorescence quenching. Moreover, the luminescent MOF exhibits efficient photocatalytic activity for aerobic cross-dehydrogenative coupling reactions mediated by visible light.

Oligomer-coated carbon nanotube chemiresistive sensors for selective detection of nitroaromatic explosives.

High-performance chemiresistive sensors were made using a porous thin film of single-walled carbon nanotubes (CNTs) coated with a carbazolylethynylene (Tg-Car) oligomer for trace vapor detection of nitroaromatic explosives. The sensors detect low concentrations of 4-nitrotoluene (NT), 2,4,6-trinitrotoluene (TNT), and 2,4-dinitrotoluene (DNT) vapors at ppb to ppt levels. The sensors also show high selectivity to NT from other common organic reagents at significantly higher vapor concentrations. Furthermore, by using Tg-Car/CNT sensors and uncoated CNT sensors in parallel, differential sensing of NT, TNT, and DNT vapors was achieved. This work provides a methodology to create selective CNT-based sensors and sensor arrays.

Highly sensitive and selective detection of 2,4,6-trinitrophenol using covalent-organic polymer luminescent probes

We have synthesized two luminescent covalent-organic polymers (COPs), which could be considered as promising luminescent probes for highly sensitive and selective detection of nitroaromatic explosives, especially for 2,4,6-trinitrophenol.

Cavitand-Based Solid-Phase Microextraction Coating for the Selective Detection of Nitroaromatic Explosives in Air and Soil

A selective cavitand-based solid-phase microextraction coating was synthesized for the determination of nitroaromatic explosives and explosive taggants at trace levels in air and soil. A quinoxaline cavitand functionalized with a carboxylic group at the upper rim was used to enhance selectivity toward analytes containing nitro groups. The fibers were characterized in terms of film thickness, morphology, thermal stability, and pH resistance. An average coating thickness of 50 (±4) μm, a thermal stability until 400 °C, and an excellent fiber-to-fiber and batch to batch repeatability with RSD lower than 4% were obtained. The capabilities of the developed coating for the selective sampling of nitroaromatic explosives were proved achieving LOD values in the low ppbv and ng kg(-1) range, respectively, for air and soil samples.

A Fluorescent Sensor for Highly Selective Detection of Nitroaromatic Explosives Based on a 2D, Extremely Stable, Metal–Organic Framework

A 2D, extremely stable, metal-organic framework (MOF), NENU-503, was successfully constructed. It displays highly selective and recyclable properties in detection of nitroaromatic explosives as a fluorescent sensor. This is the first MOF that can distinguish between nitroaromatic molecules with different numbers of NO2 groups.

Atmospheric pressure ion/molecule reactions for the selective detection of nitroaromatic explosives using acetonitrile and air as reagents

Acetonitrile vapor and air are useful reagents for the selective detection of nitroaromatic compounds using atmospheric pressure ion/molecule reactions. Reagent ions CH2CN- and CN- generated from acetonitrile, and O-*, OH- and OOH- produced from the oxygen in air, react with vapor-phase and condensed-phase nitroaromatics in the course of atmospheric pressure chemical ionization (APCI) and desorption atmospheric pressure chemical ionization (DAPCI), respectively. The homogeneous and the heterogeneous phase reactions both lead to the formation of the same anionic adducts. These adducts have characteristic fragmentation patterns upon collisional activation, which makes these two reagents valuable for the selective detection of particular nitroaromatics, including explosives present as components of complex mixtures. Complementary information is available from the two reagents because their different chemistry facilitates analyte identification. DAPCI is demonstrated to be a useful ambient detection method for nitroaromatic explosives absorbed on surfaces.